Delay-Based PUF Signal Path Selection for Low-BER Reliability
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Solution Overview
Problem
Conventional delay-based PUFs, such as ring oscillator PUFs, face issues with bit error rate (BER) due to environmental variations, leading to unreliable output and the need for costly error correction mechanisms, while being vulnerable to machine learning attacks and lacking full entropy in some configurations.
Innovation Solution
The proposed solution involves an innovative algorithm that configures multiple rounds of races between winners and losers of previous rounds to preserve maximal entropy, allowing one RO to be used in multiple pairwise comparisons, thereby reducing the bit error rate and enhancing the robustness of the PUF response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional delay-based PUFs are used, then device uniqueness is achieved, but bit error rate increases due to environmental variations
Solution Approach 1:
The patent performs preliminary configuration of optimal signal paths for PUF cells before actual PUF operation. During a configuration phase, the system pre-determines which signal paths provide the most stable and reliable outputs under various environmental conditions, storing this information for use during normal PUF operation. This preliminary action reduces bit error rates by ensuring that only the most reliable paths are used.
Solution Approach 2:
The patent changes the operational parameters of PUF cells by configuring different signal paths and pairing combinations. The system dynamically selects and switches between different signal path configurations based on pre-evaluated performance metrics, thereby adapting to environmental variations and maintaining low bit error rates across different operating conditions.
2Reliability
If error correction mechanisms are added to reduce BER, then PUF output reliability improves, but device complexity and cost increase
Solution Approach 1:
Instead of adding complex error correction mechanisms during PUF operation, the patent performs preliminary evaluation and configuration of optimal signal paths before use. The system pre-identifies and configures the best-performing PUF cell pairings and signal paths, which inherently reduces the need for additional error correction hardware and complexity.
Solution Approach 2:
The PUF system performs self-configuration by automatically evaluating its own cells and determining optimal signal paths without requiring external error correction mechanisms. The system uses its own internal resources to identify and configure the most reliable paths, thereby reducing the need for additional complexity while maintaining high reliability.
3Loss of information
If multiple rounds of races are implemented, then entropy is preserved and security improves, but test time during IC production increases
Solution Approach 1:
The patent performs the multiple rounds of racing and entropy evaluation during a preliminary configuration phase before the PUF is deployed. By completing the entropy-maximizing pairings and signal path selections in advance, the system preserves full entropy while avoiding the need for time-consuming multiple rounds during actual PUF operation, thus reducing production test time.
Solution Approach 2:
The system dynamically determines optimal pairings and signal paths through multiple evaluation rounds during configuration, then locks in these optimized settings for efficient operation. This dynamic configuration approach allows the system to achieve maximum entropy preservation without requiring continuous multiple rounds during production testing.
Data Source
AI summary
A method and electronic device for configuring a PUF, wherein: PUF cells are configured to use a signal path; determining a winner of racing pairs of PUF cells in a first round and in a second round wherein winners of the first round are raced; the first and second round are repeated for different signal paths; determining, for each signal path, a comparison metric, wherein the comparison metric is based on the count of the outputs of the PUF cells having the signal path in common; determining an optimum signal path for the PUF from the respective comparison metrics; and configuring the PUF to use the optimum signal path.